The role of transforming growth factor-β1 and oxidative stress in podoconiosis pathogenesis

Phenotypical characterization, and antibiotics susceptibility patterns of skin bacteria found in podoconiosis patients in the North West Region of Cameroon

BACKGROUND

Podoconiosis, a non-infectious disease originating from long-term exposure of bare feet to irritant red clay soil is a lifelong, disabling disease with no specific diagnostic tool, classified into 5 stages based on the severity of leg swelling (lymphoedema). Secondary bacterial infections have been suggested to cause acute dermatolymphangioadenitis (ADLA) attacks and drive disease progression. Although the North West Region of Cameroon has a proven history of podoconiosis endemicity, the bacterial composition of lymphoedema due to this condition has not been studied. Thus, this study investigated the leg bacterial diversity of patients who suffered from the lymphoedema and their susceptibility pattern to selected antibiotics.

METHODS

A cross-sectional study was carried out in which podoconiosis affected and non-lymphoedema individuals living in the same community were purposively selected. Samples were collected by swabbing the skin between the toes and around the anklebone, then cultured and sub-cultured on nutrient agar to obtain pure isolates. The cultured isolates were then morphologically and biochemically classified using microscopy and analytic profile index test kits, respectively. The disk diffusion technique was used to determine antibiotic susceptibility.

RESULTS

Thirty-three participants were recruited, and 249 bacterial isolates were characterized into 29 genera, 60 species; with 30 (50%) being gram positive rods, 19 (31.7%) gram positive cocci, and 11 (18.3%) gram negative rods. Thirteen gram positive rods, fifteen gram positive cocci, and eight gram negative rods of bacterial species were found only in podoconiosis individuals among which Cellulomonas spp / Microbacterium spp. (2.8%), Staphylococcus lentus (3.3%), and Burkholderia cepacia (4.0%) dominated. 90% (90%) of the bacterial isolates were sensitive to doxycycline, whereas ampicillin had a high level of intermediate resistance, and penicillin G had the greatest resistant profile.

CONCLUSION

Our findings show that 94 (37.8%) out of 249 described bacterial isolates were exclusively found in the legs of podoconiosis individuals, and their susceptibility pattern to antibiotics was similar to that of others.

Podoconiosis - From known to unknown: Obstacles to tackle

Podoconiosis is a non-filarial and non-communicable disease leading to lymphedema of the lower limbs. Worldwide, 4 million individuals live with podoconiosis, which is accompanied by disability and painful intermittent acute inflammatory episodes that attribute to significant disability adjusted life years (DALYs). Different risk factors like contact with volcanic red clay soil, high altitude (above 1000 m), high seasonal rainfall (above 1000 mm/year) and occupation (e.g., subsistence farmer) are associated with the risk of podoconiosis. Although podoconiosis was described to be endemic in 32 countries in Africa, parts of Latin America and South East Asia, knowledge about related genetics, pathophysiology, immunology and especially the causing molecule(s) in the soil remain uncertain. Thus, podoconiosis can be considered as one of the most neglected diseases. This review provides an overview about this non-filarial related geochemical disease and aim to present perspectives and future directions that might be important for better understanding of the disease, prospect for point-of-care diagnosis, achieving protection and developing novel treatment strategies.

With Bare Feet in the Soil: Podoconiosis, a Neglected Cause of Tropical Lymphoedema

Podoconiosis is a form of lymphoedema that occurs in tropical highland areas in genetically susceptible individuals who are exposed to irritant volcanic soils. The disease is preventable through consistent use of footwear and attention to foot hygiene; however, in endemic areas there is a strong barefoot tradition, and many cannot afford shoes. Patients with podoconiosis face significant physical disability, psychological comorbidity, reduced quality of life and experience frequent episodes of systemic illness due to acute dermatolymphangioadenitis. This review provides an overview of this important and neglected tropical skin disease and summarizes the latest research findings.

Determinants of Podoconiosis, a Case Control Study

Background

Podoconiosis is a non-filarial swelling of lower extremity endemic in tropical regions, North America and India. The etiology and pathophysiology of the disease remain unknown. The objective of this study was to identify the determinants of Podoconiosis.

Methods

Unmatched case control study design was conducted. The sample size was calculated using Epi-info soft ware: 95% CI, 85% power, control to case ratio of 2:1, expected frequency of barefoot among controls 50%, odds ratio of 1.5 and non-response rate of 10% yielding 1148 study participants. Binary logistic regression was used to identify the determinants of Podoconiosis.

Results

A total of 1113 study participants (379 cases and 734 controls) were included giving for a response rate of 96.95%. Positive family history (AOR, 2.81 [95% CI: 1.7–4.64]), bare foot (AOR, 3.26 [95% CI: 2.03–5.25]), poor foot hygiene (AOR, 2.68 [95 CI: 1.72 – 4.19]) increase the risk of Podoconiosis. Female gender (AOR, 0.26 [95% CI: 0.15–0.44]), good housing condition (AOR, 0.17 [95% CI: 0.1–0.3]), medium income (AOR, 0.12 [95 % CI: 0.07– 0.22]) and primary education (AOR, 0.02 [95% CI: 0.01–0.04]) decrease the risk of Podoconiosis.

Conclusion

Podoconiosis control and prevention programmes should involve the low income and uneducated populations.

Involvement of Hookworm Co-Infection in the Pathogenesis and Progression of Podoconiosis: Possible Immunological Mechanism

Podoconiosis is an endemic, non-infectious, geochemical and non-filarial inflammatory cause of tropical elephantiasis. The immunology of podoconiosis is not yet expressly understood. In spite of this, co-infection and co-morbidity with the infectious, soil-transmitted hookworm disease that causes iron deficiency anemia has been found to be predominant among affected individuals living in co-endemic settings, thus creating a more complex immunological interplay that still has not been investigated. Although deworming and iron-rich nutrient supplementation have been suggested in podoconiosis patients living under resource-poor conditions, and it is thought that hookworm infection may help to suppress inflammatory responses, the undisputed link that exists between a non-infectious and an infectious disease may create a scenario whereby during a co-infection, treatment of one exacerbates the other disease condition or is dampened by the debilitation caused by the other. In this paper, we elaborate on the immunopathogenesis of podoconiosis and examine the possible immunological dynamics of hookworm co-infection in the immunopathology of podoconiosis, with a view toward improved management of the disease that will facilitate its feasible elimination.

Podoconiosis, trachomatous trichiasis and cataract in northern Ethiopia: A comparative cross sectional study

BACKGROUND

Rural populations in low-income countries commonly suffer from the co-morbidity of neglected tropical diseases (NTDs). Podoconiosis, trachomatous trichiasis (both NTDs) and cataract are common causes of morbidity among subsistence farmers in the highlands of northern Ethiopia. We explored whether podoconiosis was associated with cataract or trachomatous trichiasis (TT) among this population.

METHODS

A comparative cross-sectional study was conducted in East Gojam region, Amhara, Ethiopia in May 2016. Data were collected from patients previously identified as having podoconiosis and from matched healthy neighbourhood controls. Information on socio-demographic factors, clinical factors and past medical history were collected by an interview-administered questionnaire. Clinical examination involved grading of podoconiosis by examination of both legs, measurement of visual acuity, direct ophthalmoscopy of dilated pupils to grade cataract, and eyelid and corneal examination to grade trachoma. Multiple logistic regression was conducted to estimate independent association and correlates of podoconiosis, TT and cataract.

FINDINGS

A total of 700 participants were included in this study; 350 podoconiosis patients and 350 healthy neighbourhood controls. The prevalence of TT was higher among podoconiosis patients than controls (65 (18.6%) vs 43 (12.3%)) with an adjusted odds ratio OR 1.57 (95% CI 1.02-2.40), p = 0.04. There was no significant difference in prevalence of cataract between the two populations with an adjusted OR 0.83 (95% CI 0.55-1.25), p = 0.36. Mean best visual acuity was 0.59 (SD 0.06) in podoconiosis cases compared to 0.44 (SD 0.04) in controls, p<0.001. The proportion of patients classified as blind was higher in podoconiosis cases compared with healthy controls; 5.6% vs 2.0%; adjusted OR 2.63 (1.08-6.39), P = 0.03.

CONCLUSIONS

Individuals with podoconiosis have a higher burden of TT and worse visual acuity than their matched healthy neighbourhood controls. Further research into the environmental and biological reasons for this co-morbidity is required. A shared approach to managing these two NTDs within the same population could be beneficial.

[Podoconiosis, a society and medical community neglected disease]

Podoconiosis, mossy foot or endemic non-filarial elephantiasis, is a geochemical disease that causes lower limb lymphedema; it is directly related to walking barefoot over soils of volcanic origin, in areas with a high pluviometric annual index. It has a specific geographical distribution, affecting around 5% population in areas where it is endemic. It is debilitating and disfiguring disease, which frequently leads to social margination. Podoconiosis is totally preventable and, once a diagnosis is established, it may improve with simple therapeutic measures.

Modelling environmental factors correlated with podoconiosis: a geospatial study of non-filarial elephantiasis

INTRODUCTION

The precise trigger of podoconiosis - endemic non-filarial elephantiasis of the lower legs - is unknown. Epidemiological and ecological studies have linked the disease with barefoot exposure to red clay soils of volcanic origin. Histopathology investigations have demonstrated that silicon, aluminium, magnesium and iron are present in the lower limb lymph node macrophages of both patients and non-patients living barefoot on these clays. We studied the spatial variation (variations across an area) in podoconiosis prevalence and the associated environmental factors with a goal to better understanding the pathogenesis of podoconiosis.

METHODS

Fieldwork was conducted from June 2011 to February 2013 in 12 kebeles (administrative units) in northern Ethiopia. Geo-located prevalence data and soil samples were collected and analysed along with secondary geological, topographic, meteorological and elevation data. Soil data were analysed for chemical composition, mineralogy and particle size, and were interpolated to provide spatially continuous information. Exploratory, spatial, univariate and multivariate regression analyses of podoconiosis prevalence were conducted in relation to primary (soil) and secondary (elevation, precipitation, and geology) covariates.

RESULTS

Podoconiosis distribution showed spatial correlation with variation in elevation and precipitation. Exploratory analysis identified that phyllosilicate minerals, particularly clay (smectite and kaolinite) and mica groups, quartz (crystalline silica), iron oxide, and zirconium were associated with podoconiosis prevalence. The final multivariate model showed that the quantities of smectite (RR = 2.76, 95% CI: 1.35, 5.73; p = 0.007), quartz (RR = 1.16, 95% CI: 1.06, 1.26; p = 0.001) and mica (RR = 1.09, 95% CI: 1.05, 1.13; p < 0.001) in the soil had positive associations with podoconiosis prevalence.

CONCLUSIONS

More quantities of smectite, mica and quartz within the soil were associated with podoconiosis prevalence. Together with previous work indicating that these minerals may influence water absorption, potentiate infection and be toxic to human cells, the present findings suggest that these particles may play a role in the pathogenesis of podoconiosis and acute adenolymphangitis, a common cause of morbidity in podoconiosis patients.

Podoconiosis and soil-transmitted helminths (STHs): double burden of neglected tropical diseases in Wolaita zone, rural Southern Ethiopia

Background

Both podoconiosis and soil-transmitted helminth (STH) infections occur among barefoot people in areas of extreme poverty; however, their co-morbidity has not previously been investigated. We explored the overlap of STH infection and podoconiosis in Southern Ethiopia and quantified their separate and combined effects on prevalent anemia and hemoglobin levels in podoconiosis patients and health controls from the same area.

Methods and Principal Findings

A two-part comparative cross-sectional study was conducted in Wolaita zone, southern Ethiopia. Data were collected from adult patients presenting with clinically confirmed podoconiosis, and unmatched adult neighborhood controls living in the same administrative area. Information on demographic and selected lifestyle factors was collected using interviewer-administered questionnaires. Stool samples were collected and examined qualitatively using the modified formalin-ether sedimentation method. Hemoglobin level was determined using two different methods: hemoglobinometer and automated hematology analyzer. A total of 913 study subjects (677 podoconiosis patients and 236 controls) participated. The prevalence of any STH infection was 47.6% among patients and 33.1% among controls (p<0.001). The prevalence of both hookworm and Trichuris trichiura infections was significantly higher in podoconiosis patients than in controls (AOR 1.74, 95% CI 1.25 to2.42, AOR 6.53, 95% CI 2.34 to 18.22, respectively). Not wearing shoes and being a farmer remained significant independent predictors of infection with any STH. There was a significant interaction between STH infection and podoconiosis on reduction of hemoglobin level (interaction p value = 0.002).

Conclusions

Prevalence of any STH and hookworm infection was higher among podoconiosis patients than among controls. A significant reduction in hemoglobin level was observed among podoconiosis patients co-infected with hookworm and ‘non-hookworm STH’. Promotion of consistent shoe-wearing practices may have double advantages in controlling both podoconiosis and hookworm infection in the study area.

Podoconiosis and soil-transmitted helminth infections are neglected tropical diseases occurring among barefoot people in areas of extreme poverty, and both promote poverty through effects on education, economic productivity and disability. In Ethiopia, little research on podoconiosis has been conducted and though social, economic and psychological burdens have been described, no previous study has investigated co-morbidity with other neglected tropical diseases. We therefore aimed to explore the overlap of soil-transmitted helminth infection and podoconiosis in southern Ethiopia by comparing the prevalence of STH infections among podoconiosis patients and healthy controls. We also demonstrate the separate and combined impact of STH infection and podoconiosis on hemoglobin level. We found that the prevalence of any STH and hookworm infection was higher among podoconiosis patients than among controls. A significant reduction in hemoglobin level was observed among podoconiosis patients co-infected with hookworm and ‘non-hookworm STH’. Based on the current findings, integrated control programs that include targeted anthelminthic distribution to control STH among podoconiosis patients, and promotion of consistent shoe-wearing practices are recommended in the study area.